1. Field of the Invention
Embodiments disclosed herein relate to downhole tools, particularly setting tools for hydraulic liners and other hydraulic actuated devices. More specifically, embodiments disclosed herein relate to setting tools that actuate hydraulic liner hangers in deviated wellbores.
2. Background Art
Typically, liners are used below casing in wellbores to extend the length of the casing. A liner is a section of smaller casing that is suspended downhole in existing casing. In most cases, the liner extends downwardly into an open hole and overlaps the existing casing by approximately 200-400 ft. In certain application, the liner may be cemented in place. A conventional liner hanger is used to attach or hang liners from the internal wall of a casing segment. Hydraulic liner hangers have been preferred by operators in deviated wellbores over mechanical liner hangers. This is because deviation of the wellbore makes it less certain that the mechanical hanger mechanism will be properly actuated in a deviated wellbore. In this instance hydraulic liners provide advantages over mechanical hangers, because hydraulic hangers may not require mechanical movement of the pipe or tubular.
In conventional designs, the liner with a setting tool is lowered into position, and pressure within the setting tool is used to set the hydraulic liner hanger through a lateral port therein. In some designs, the flow passage through the setting tool is obstructed at its lowermost end so the applied pressure in the setting tool properly reaches the hydraulic liner hanger. Other designs place the obstruction for the setting tool near the bottom of the liner to allow a cement wiper plug to pass completely through the liner to remove residual cement therefrom. If the residual cement is not removed, cutting or grinding operations may be required to remove excess cement within the liner.
Some aspects of using a conventional setting tool may lengthen the time required to complete the placement and cementing of a liner. In addition to an increase in completion time, other setting tool designs are subject to inadvertent damage within the tool. For example, collet-type valve seats have been used in applications where the drop ball seats on relatively short upwardly directed collet fingers, thus compressing the collet fingers when the ball is seated. A shear pin release permits a shift of the fingers to a location where the collet fingers are expanded to release the ball member. The collet fingers are typically short, thereby preventing the compressive forces from damaging them. (The design, thus, requires that the fingers have little resilience and prevents them from fully expanding unless a large diameter ball is used. In addition to damaging the tool, using a large diameter ball raises the possibility of prematurely actuating a wiper plug upon release.) A collet mechanism is also prone to damaging fins of a pump-down plug or dart by folding the fins backwards as they pass through the unsupported slots of the collet. Additionally, fluid cuts as it passes around the fins and through the slots.
In a system where the end of the liner with a setting tool is located in a non-vertical location, such as a deviated or horizontal section of well bore, other problems arise. In these instances it can be extremely difficult, and sometimes not possible, to obtain seating of a ball or an obstructing device in a small, centrally located valve seat opening at the lower end of a liner. In such a design, the valve seat has a convex upper surface, as shown in, for example, U.S. Pat. No. 5,553,672. In this design, as the ball rolls along the inner diameter of the tool, gravity may move the ball into a dead fluid area that is adjacent to the seat. In order to seat the drop ball, the ball must be lifted off of the low side of the tool and moved to the center of the valve with the fluid flow. This process can be time constraining and difficult to accomplish.
Accordingly, there exists a need for a setting tool that provides a pressure differential for actuating downhole tools that includes an improved ball valve assembly.